Portable heart monitors and blood pressure monitors have been known. Some of these monitors incorporate watch functions and are worn on the wrist of the user. The display on the watch indicates time and or date. Furthermore, the user selects a certain mode to monitor either blood pressure or heartbeat. For example, as disclosed in Japanese Patent Publication Hei 8-299292, after the user selects a heartbeat monitor mode, the display indicates a number of heartbeats per minute. However, to measure heartbeats, a small cuff must be additionally worn on a finger tip by the user.
Japanese Publication 62-292137 discloses another example of a blood pressure monitor. A wrist watch incorporates a blood pressure monitor. An inflatable tubular cuff has been incorporated in the wrist band or the straps. The cuff is connected to a pressure measuring chamber, and a pressure sensor is located in the pressure chamber. Upon selecting a blood pressure measuring mode, the user manually pumps air into the cuff in order to inflate the cuff against the arteries in the wrist. The intermittently inflated cuff contains air whose pressure is measured by the pressure sensor. The measured pressure change is calculated to display the blood pressure at the display.
As described above, in prior art, to measure either blood pressure or heartbeat, the user must perform additional tasks. According to the above examples, the user must wear an additional finger piece for the heartbeat measurement or must pump the air into the cuff for the blood pressure measurement.
In addition, the above described prior,art techniques also encounter noise. One source of the noise is associated with the movements of the wrist. In order to measure the blood pressure, the cuff must be sufficiently inflated around the entire circumference of the wrist so as to detect the pressure change in the arteries. Because of the snug contact, certain wrist movements also cause undesirable and indistinguishable pressure change. Another source of the noise is associated with small high-frequency components that are not caused by arterial movement.
For the above reasons, it remains desired to develop a method, device and system to measure the arterial movement by a wearable watch device without any additional component and at a high accuracy.